Abstract

Zebra stripes have traditionally been thought of as an adaptation against detection by vertebrate predators, such as lions and hyaenas. A different hypothesis is suggested: that the stripes are an adaptation against visually orienting biting flies and act by obliterating the stimulus presented by a large dark form, which is important in host-finding by many Diptera. This hypothesis is supported by some indirect evidence and by a field experiment which compares fly catches on moving and stationary black, white and striped models. Striped models caught significantly fewer tsetse and other flies than solid black or white models, but this difference was much reduced in the presence of olfactory attractants.